Combined multiplying and dividing machine



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COMBINED MULTIPLYING AND DIVIDING MACHINE Filed Feb. 11, 1942 19 Sheets-Sheet 19 #L a l M INVENTOR 533 ATTo'RNEY Patented May 8, 1945 UNITED STATES PATENT OFFICE comma!) MULTIPLYING AND mvmmo MACHINE James W. Bryce, Glen Ridge, N. J., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application February 11, 1942, Serial No. 430,324

4 Claims.

This invention relates generally to calculating machines which are provided with both multiplying and dividing mechanisms and particularly to the type of machine wherein the result of the computation secured by the operation of one of the mechanisms is checked by a computation performed by the other mechanism. The checking of such computations is particularly useful and advantageous in record controlled machines wherein the computation result is recorded upon the record containing the original factors and since the accuracy of the computation result is vital in the accounting system in which the results of the computations are utilized, the checking operations are necessary and particularly desirable in accounting systems where extreme accuracy in results is required.

According to arrangements previously devised, it was proposed to provide a machine which would enable a computation of one type to be performed by either a dividing or multiplying mechanism to secure a computation result, either product or quotient according to the selected computation, and record the result on the card. It was proposed to have the factors of the computation, namely the multiplicand and multiplier on multiplying, or the dividend and divisor for the computation of division, together with the recorded product or quotient result taken from the card, then effect the subsequent recomputation by re-running the card through the machine. The change for the recomputation could not be efiected automatically and required re-- conditioning of the machine for the recomputation by manual intervention which consisted primarily of replugging. By the provision of suitable checking devices, the correctness of the recorded quotient or product upon the record at the termination of the original combination was ascertained. If the computation result recorded either quotient or product) was found incorrect, the operator of the machine was accordingly signaled so that the incorrectly recorded card could be removed and the computation again performed to secure the correct computation result. For each inaccuracy found in the computation result, a card was lost and while the value of the card per se was of no material consequence, yet it required the reperforating of a card for the factors of the computation.

It is also contemplated in Patent No. 2,206,218 to R. Blakely, dated July 2, 1940, to provide a machine which will check the product result of a multiplying computation by a subsequent recomputation of the same type without, however,

requiring that the product result be recorded and the cards be re-run through the machine. Checking devices were also provided to check the newly acquired product before it is recorded upon the card, against the subsequently derived product result. Upon agreement, product recording would then ensue and by this arrangement, the reperforating of a card upon locating an incorrectly derived product was avoided. However, the recomputation for checking purposes was performed by the same type of computation, that is, an original multiplying operation was automatically followed by a subsequent multiplying operation. While, as stated in this patent, checking multiplying is effected with the factor entry relations reversed so as to provide difierent operations of the computing mechanisms involved, nevertheless there are mechanisms which are commonly operated for the original and subsequent computation in the same way, and furthermore, the checking of the originally derived product against the newly computed product does not provide for the extreme accuracy required in checking.

Accordingly, the present invention provides to overcome the disadvantages of the previous arrangements by effecting a recomputation by a different type of computation and since the same calculating mechanisms do not operate in the original and recomputation, the desired efliciency in checking is attained. Furthermore, in the actual checking operation, diiferent value representations are compared rather than the comparison of supposedly the same values, such as the product, as was proposed in the aforementioned Patent No. 2,206,218.

The principal object of the present invention is, therefore, to provide an arrangement which will effect a computation of one type which is secured by one form of computing mechanism and then automatically perform without manual intervention a computation of another type under control of one of the factors for the original computation and the previously derived computation result.

More specifically, it is an object of the invention to provide an arrangement of the type just described with checking devices which will determine whether the computation result of the original computation is correct.

A still further object is to suppress the recording of the computation result upon the record which is derived from one computing mechanism until the termination of the operation of the second computing mechanism and the operation of 

